Emissions standards are requirements that set specific limits on the amount of pollutants that can be released into the environment. The first U.S. federal standards for new non-road diesel engines were adopted in 1994, and the most recent “Tier 4” standards, to be phased in by 2015, are even more stringent. In particular, Tier 4 standards for non-road diesel engines, such as those used on mine haul trucks and other equipment often used in the mining industry, require that emissions of particulate matter (PM) and nitrogen oxides (NOx) be further reduced by 90% from current allowable levels.
In order to comply with these standards, new non-road diesel engines often include an exhaust gas aftertreatment system, e.g., selective catalytic reduction, to reduce NOx emissions. This particular type of exhaust gas aftertreatment involves the injection of diesel exhaust fluid (DEF) into the exhaust as it moves though the engine, where it vaporizes and decomposes to form ammonia and carbon dioxide. The NOx are catalytically reduced by the ammonia into water and nitrogen, which are both harmless, and are released through the exhaust. In conjunction with the exhaust gas aftertreatment system, new non-road diesel engines typically include control technologies that limit the power output of the engine if emissions exceed set guidelines. In particular, the engines may include a controller having a built in warning and override system that is configured to automatically de-rate the engine (performance de-rates) to prevent operation without proper emission control. For example, the controller may be configured to automatically de-rate the engine when sensed emission levels exceed allowable limits, such as when a supply of DEF is exhausted, leading to a spike in NOx emission.
Existing emission control systems for non-road diesel engines, however, have the potential to create significant vehicle deration at undesirable times, such as when a loaded haul truck is operating on grade in a surface mine. As will be readily appreciated, automatically de-rating on grade, especially without adequate warning to a driver of the haul vehicle, may compromise safety and may also slow mine production. As such, it is desirable to provide a driver alert/warning and de-rate control system that improves operational safety and limits production impact.